Self-contained honeycomb structure from flexible film strips and method for its production

ABSTRACT

A honeycomb structure with a plurality of flexible material strips which are arranged next to one another and are connected to one another is presented. The material strips have a corrugated shape with U-shaped cross section of essentially straight, vertical partial areas ( 3 ) and curved, horizontal partial areas ( 2 ). The material strips are connected to one another at contact points ( 4 ) of the straight, vertical partial areas. In addition, a device for manufacturing a honeycomb has welding sections ( 6 ). The flexible material strips ( 9 ) are guided by the welding sections ( 6 ), where the material strips are welded to one another by means of a comb-like finger system ( 10 ). The finger system or the welding sections are laterally displaced by two sections and by a pressing operation taking place between the finger and the welding section. This presses two material strips onto a heated welding wire ( 7 ), which leads to the thermal connection of the material strips.

FIELD OF THE INVENTION

The present invention pertains to a honeycomb structure from flexiblematerial strips, which are connected to one another, so that aself-supporting honeycomb structure is formed, as well as to a processfor manufacturing same.

BACKGROUND OF THE INVENTION

Corresponding honeycomb structures are used, among other things, astransparent or opaque heat insulation, as filler material for partitionsor as the core material in the manufacture of sandwich boards.

If the honeycombs are used as heat insulation, low density is importantin order to obtain good insulation values. If the honeycombs shall beused for sandwich boards, high compressive strength combined with highshear strength is necessary.

Similar honeycomb structures are described in the AuslegeschriftDT2231959 B2 and in the Offenlegungsschrift DE 197 03 961 A1.

The Auslegeschrift DT 2231959 B2 describes a honeycomb from corrugated,rigid strips, which have an inherent stability, so that they can bestacked upon one another, and form a self-supporting structure, withoutthe strips being welded or bonded to one another. The prerequisite forthis is that die arches of the corrugations have such an arrangementthat the shortest free distance between two adjacent peaks of thecorrugation in each strip is smaller than the greatest free width of thevalley of the corrugation (therefore, the corrugated strips cannot hepushed into one another).

Honeycombs of this type cannot be manufactured from flexible materialstrips, because a flexible strip cannot be bent into a rigid corrugatedshape.

Honeycombs of this type are used as the core for sandwich boards made ofmetal, e.g., in the manufacture of aircraft.

A honeycomb structure made of flexible film strips is described in theOffenlegungsschrift DE 197 03 961 A 1, wherein the film strips arewelded onto one another in the corrugated form, so that aself-supporting honeycomb is formed. The principal difference from DT2231959 B2 is that flexible strips are used here and a honeycomb isgenerated only when the strips arc connected lo one another by weldingor bonding in the transition area from the horizontal and verticalpartial areas of the corrugated strips arranged one on top of another.The residual stress (restoring behavior) of the flexible strips ensuresthat the honeycomb is more rigid and stable than a honeycomb made ofpre-corrugated webs. A honeycomb is formed which is similarly bulged asthe honeycomb from DT 2231959 B2 and has a nearly isotropic behaviorwhether it is loaded mechanically in the vertical or horizontaldirection. One drawback is that this honeycomb cannot be compressedwithout distortions developing in the structure. Another drawback ofthis honeycomb which is linked with the process is the opticallynonuniform edge structure. Since individual film strips are welded toone another, the overhanging film strips overlap at the lateral edges inparallel to the direction of production. To obtain a clean edge closure,an edge strip must be cut off, as a result of which drawbacks arise interms of costs due to clipping.

SUMMARY AND OBJECTS OF THE INVENTION

The basic object of the present invention is to improve a honeycomb ofthe type mentioned in the introduction such that a self-supportinghoneycomb is formed from flexible strips, which has a clean edgestructure and can be compressed in a direction in parallel to thedirection of production.

According to the present invention a self-supporting honeycomb isprovided manufactured from flexible strips, which honeycomb consists,however, contrary to DE 197 03 961 A1, of horizontal, bent partial areasarranged at right angles to one another in parallel to the directionalof production and straight vertical partial areas.

In addition, the bonded or weld scam of the honeycomb being describedhere is located at straight vertical partial areas rather than of thehorizontal and vertical partial areas of the corrugated strips arrangedone on top of another (or in other words, at the edges of theparallelepipedic cavities), as in DE 197 03 961.

These features, which are essential for the present invention, arecharacteristic of a compressible honeycomb, and the advantage is aboveall that a compressed honeycomb can be transported at a substantiallylower cost. Moreover, there are applications, e.g., as heat insulation,which require a small hole diameter, which can be obtained simply bycompressing the honeycomb. Minimization of the hole diameter means amaximization of the heat insulation factor (k value) for a honeycomb.

The honeycomb displays different behaviors under mechanical loading inthe horizontal and vertical directions. Compression in parallel to thedirection of production is possible without the structure of thehoneycomb being distorted. A clean edge is formed on both sides of thehoneycomb along the direction of production, because the respectiveouter film is welded endlessly to the honeycomb.

According to another aspect of the invention, a device is provided withwhich a self-supporting honeycomb structure can be manufactured.

The device has a welding head, which comprises a plurality of weldingsections or webs arranged in parallel to and at uniformly spacedlocations from one another, all of which are equipped with a weldingwire on the front side. Flat feed elements, which can be displacedforward and backward in parallel to the webs, are in contact with thelateral surfaces of the welding webs. There is a small gap between thefeed elements, through which the film strips can be guided. In addition,the device has a comb with individual fingers, which can be moved intoand withdrawn from the honeycomb structure in front of the welding webs.The welding head and the finger comb are displaceable in parallel to oneanother.

In addition, the welding head and the finger comb can be pressed againstone another.

The necessary U-shaped corrugated structure of the film strips isproduced with the device by the lateral displacement of the welding headand the comb, and the film strips are subsequently welded to one anotherat the vertical partial areas.

Not only plastic films, but all types of flexible material strips can beconnected to one another with the device, the only requirement being theweldability of the material.

The honeycomb structure according to the present invention as well asthe process steps for manufacturing this honeycomb structure will beexplained in greater detail below on the basis of the drawings attached.The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a top view of a honeycomb structure according to the presentinvention;

FIG. 2 is top view of the device for manufacturing the honeycombstructure according to FIG. 1 showing an individual process step;

FIG. 3 is top view of the device for manufacturing the honeycombstructure according to FIG. 1 showing another process step;

FIG. 4 is top view of the device for manufacturing the honeycombstructure according to FIG. 1 showing another process step;

FIG. 5 is top view of the device for manufacturing the honeycombstructure according to FIG. 1 showing another process step;

FIG. 6 is top view of the device for manufacturing the honeycombstructure according to FIG. 1 showing another process step;

FIG. 7 is top view of the device for manufacturing the honeycombstructure according to FIG. 1 showing another process step; and

FIG. 8 is top view of the device for manufacturing the honeycombstructure according to FIG. 1 showing still another process step.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows honeycomb structure according to the present invention. Theconnection of the individual film webs, to the points designated by 4,is possible by bonding or, as was described above, by preparing a weldseam extending at right angles to the film web. The honeycomb structureis in general designated by reference number 1 with a horizontal partialarea 2 of the structure. Vertical partial areas 3 and welded connectionpoints or lines are shown in FIG. 1. A clean corrugated edge structure 5results as there is no waste material generated along the edges.

FIGS. 2 to 8 show the device for manufacturing the honeycomb structureaccording to FIG. 1. An example according to the present invention willbe described below. The example includes individual process step formanufacturing a honeycomb structure with film webs using weldedconnections.

FIG. 2 shows the welding head with the welding webs 6, which areequipped with welding wires 7 on the front side, and with the flat feedelements 8, which are in contact with the welding webs.

The welding head is located in the starting position, and the individualfilm strips 9 are inserted between the narrow gaps of the feed elements.

FIG. 3 shows the first processing step. The feed elements 8 move forwarduntil they project from the welding head over a certain distance. Thefinger comb 10 now moves between the feed elements and thus into thefilm strip until it stands in front of the welding head over the fullwelding height.

The feed elements 8 move back again behind the welding planecorresponding to FIG. 4. The welding head and the finger comb 10 are nowdisplaced in parallel horizontally by an amount or distance 14corresponding to twice the distance between two welding spots. The firstwelding of the film takes place in this position, the welding head andthe welding fingers being pressed onto one another as indicated by arrow15. The welding wires 11 contact and thermally weld the film pressedthereon by the flexible welding pads 12. It is also possible to equipthe fingers with heating wires together designated 13, so that heat maybe applied from one or more sides of the film.

According to FIG. 5 the fingers 10 again move out of the film strip 9.The feed elements 8 then move forward and the film structure weldedtogether is fed. The welding head again moves back into the startingposition by an amount corresponding to twice the space between twowelding spots.

The fingers 10 then move again into the film structure corresponding toFIG. 6. FIG. 7 shows how the feed elements 8 move back behind thewelding plane.

The welding head and the fingers 10 are now displaced in oppositedirections. Pressing on of the welding head with the fingers 10 and thefilm welding operation will again take place.

The fingers 10 then move again out of the film structure according toFIG. 8 and the cycle of steps begins anew with step 1 (FIG. 3).

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A device for manufacturing a honeycomb structurewith a plurality of flexible material strips arranged next to oneanother, the strips being connected to one another, the material stripshaving a corrugated shape with a U-shaped cross section of essentiallystraight vertical partial areas and curved horizontal partial areas, thematerial strips being connected to one another at contact lines of thestraight vertical partial areas, the device comprising: laterallydisconnected welding sections equipped with heated welding wires, bywhich said flexible material strips; are guided, said material stripsbeing welded to one another by means of a comb-like finger system,moveable into the material strips to generate a welding surface, and tofold the material strips to a honeycomb structure by a lateraldisplacement of either the finger system or the welding sections and toperform a pressing-on motion by either the finger system or the weldingsections, to press two material strips onto a heated welding wire,thermally connecting the material strips; and feed elements generating afeed motion of the honeycomb by a distance of one honeycomb holediameter whenever a welding cycle of one honeycomb layer is performedafter the finger system has moved out of the honeycomb layer after thewelding of the material strips is finished, and the finger system or thewelding sections being laterally displaced by; a distance correspondingto twice the distance between two welding spots and wherein the fingersystem or the welding sections perform a lateral displacement by thesame distance during the first welding cycle in one direction and duringthe following welding cycle in the opposite direction.
 2. A device inaccordance with claim 1, wherein said fingers of are equipped with aheating wire for welding together the material strips.
 3. A device inaccordance with claim 1, wherein both said welding sections and saidfingers are equipped with a heating wire for welding together thematerial strips.
 4. A device in accordance with claim 1, wherein thefeeding of the honeycomb can be accomplished by means of said feedelements between said welding sections, but also with a second fingersystem which moves into the completely welded honeycomb and subsequentlyperforms a feed motion.
 5. A device for manufacturing a honeycombstructure in accordance with claim 1, further comprising: flexiblewelding pads on fingers of said finger system.
 6. A device formanufacturing a honeycomb structure with a plurality of flexiblematerial strips arranged next to one another, the strips being connectedto one another, the material strips having a corrugated shape with aU-shaped cross section of essentially straight vertical partial areasand curved horizontal partial areas, the material strips being connectedto one another at contact lines of the straight vertical partial areas,the device comprising: welding sections arranged spaced relative to eachother, said material strips being feedable between said welding sectionsby feed elements; and a finger system corresponding to said weldingsections, said finger system being laterally displaceable relative tosaid welding sections displacing said material strips after feeding bysaid feed elements, to form U-shaped sections, subsequent to saidlateral displacing of said material strips, said finger system pressingsaid material strips against said welding sections between a heatingwire on one or both of said welding sections and said finger system toform a thermal weld between two of said material strips, said fingersystem then retracting from between said material strips, moving in alateral direction opposite to that of the last lateral displacement,inserting between said material strips displaced by two weldingsections, and repeating said steps but with a displacement in anopposite lateral direction beginning with said feed elements feedingsaid material strips.
 7. A device for manufacturing a honeycombstructure in accordance with claim 6, further comprising: flexiblewelding pads on said fingers of said finger system.
 8. A method offorming a U-shaped honeycomb structure from a plurality of materialstrips, the method comprising: a) feeding material strips by means offeed elements between welding sections; b) inserting fingers of a fingersystem, with said fingers corresponding to said welding sections,between said material strips and laterally displacing said fingers withsaid material strips by two welding sections relative to said weldingsections; c) moving said finger system against said welding sectionspressing two layers of said material strips together between one or moreof said welding sections and said fingers; (d) heating said layers ofmaterial strips pressed together to form a thermal weld; e) withdrawingsaid fingers from between said material strips; and f) continuing toperform steps a-e, while alternating the lateral displacement directionin step b each time it is performed, until a desired amount of honeycombstructure is produced.